Voyager: What are the immediate and future consequences of polluting a fish's habitat?

A: The answer to this question depends on what kind of pollution it is, how much of it there is and what kind of fish it is. However, most of the time, there are a few likely results.

If the pollution is harmful to the fish or strongly affects it, it will leave its habitat. When that happens, there won’t be any fish left there and that will affect the other animals and plants by changing the balance in the fish’s community, or ecosystem. For example, the plants that the fish used to eat will become overgrown because the fish isn’t there to eat them. The fishes that left will be safe and healthy, but their original home might not be the same due to the pollution and the changes in the habitat. It will need time to recover.

Changes can also happen if the pollution kills a fish’s prey, without affecting the fish itself. Without available food, the fish will leave the habitat or if it is unable to leave, it might become weak with no more food to eat. That could make it an easy target for bigger predators. The fishes will then die.

In the same way, if the fish’s habitat is destroyed by the pollution, it might not be able to find a safe place to lay its eggs and birth its babies. When this happens, adult fishes and their young are at risk. A population of fish is healthy only if it can reproduce and “provide” new individuals and keep the ecosystem healthy.

If the pollution isn’t affecting fishes directly, it could reach them indirectly. Pollutants in the habitats will be accumulated through the food chain, eventually reaching the fishes. The fishes will look healthy, but they will eat contaminated food. The danger is that those fishes are then loaded with contaminants, and can be eaten by predators, who can become sick and even die. This could even include people who eat contaminated fishes.

The consequences of pollution can be very serious. The best prevention is to avoid any kind of pollution! You can do your part by putting trash where it belongs, keeping litter or other pollutants out of storm drains and learning more about your local environment.

Dimitri Deheyn, Marine Ecotoxicologist
Marine Biology Research Division
Scripps Institution of Oceanography, UC San Diego